﻿using System;
using System.Globalization;
using System.Net;
using System.Text;
using System.Text.RegularExpressions;
using Xpedite.Extensions;

/* Copyright (c) 2010 CBaxter
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), 
 * to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, 
 * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 
 * IN THE SOFTWARE. 
 */

namespace Xpedite.Resources.Loaders
{
  internal class WebResourceLoader : IResourceLoader
  {
    private static readonly Regex ContentTypeCharsetPattern = new Regex(@";\s*charset\s*=\s*(?<encoding>.+);?");
    private readonly IResourceUrl _resourceUrl;

    public WebResourceLoader(IResourceUrl resourceUrl)
    {
      Verify.NotNull(resourceUrl, "resourceUrl");

      _resourceUrl = resourceUrl;
    }

    public ResourceData LoadData()
    {
      using (WebClient webClient = new WebClient())
      {
        webClient.UseDefaultCredentials = true;

        Byte[] bytes = webClient.DownloadData(_resourceUrl.ToUri().AbsoluteUri);

        return new ResourceData
        {
          Bytes = bytes,
          Encoding = GetEncoding(webClient, bytes),
          LastModified = GetLastModifiedDateTime(webClient)
        };
      }
    }

    private static DateTime GetLastModifiedDateTime(WebClient webClient)
    {
      DateTime lastModified;

      return DateTime.TryParseExact(webClient.ResponseHeaders[HttpResponseHeader.LastModified], DateFormat.RFC1123, CultureInfo.CurrentCulture, DateTimeStyles.None, out lastModified)
             ? lastModified
             : DateTime.UtcNow.Date;
    }

    private static Encoding GetEncoding(WebClient webClient, Byte[] bytes)
    {
      Match match = ContentTypeCharsetPattern.Match(webClient.ResponseHeaders[HttpResponseHeader.ContentType] ?? String.Empty);
      return match.Success ? Encoding.GetEncoding(match.Groups["encoding"].Value) : bytes.DetectEncoding();
    }
  }
}